Development of a serial link structure/parallel wire system for a force display

A type of robot system for a force display which has a serial link structure driven by a parallel mechanism is proposed. This system consists of serially jointed links as usual industrial robots and parallel wires that are driven by actuator units located on the base. Therefore, there are advantages of both a serial link structure robot and a parallel wire driven robot, such as large work space, high speed, safety, and so on. In previous analysis of the parallel wire driven mechanism, the object is a single rigid body, so that the driving principle in such cases was obvious based on a theory of "vector closure". However, in the case of the proposed system, the driving principle has not been cleared, because the mechanism is very complicated. In this paper, we show static conditions for each joint of the proposed system based on partial vector closure corresponding to the serial link structure/parallel wire system. Moreover, a prototype of the force display system is developed by using the conditions. Finally, the usefulness of the proposed system is demonstrated through some experimental results.